act up
To misbehave; to cause trouble.
Meaning adapted from Wiktionary, available under CC BY-SA 4.0.
“The children always act up when they're tired.”
“My computer started to act up right before my important video call.”
“The old car had behaved perfectly for years, but now it was beginning to act up at every traffic light.”
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act of Congress
An authorization that is extremely difficult to obtain, especially in a timely fashion.
- 02
act one's age
To behave in a manner appropriate to one's age.
- 03
act one's age, not one's shoe size
Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).
- 04
act out
To perform something specific.
- 05
act the hypocrite
To behave deceitfully or hypocritically; to dissemble.
- 06
clean up one's act
To reform; to improve one's habits.
- 07
get into the act
To participate in an activity, especially a successful or attractive one.
- 08
get one's act together
To become serious, organized, worthwhile, etc.
Last updated August 10, 2026